Voltage level correspond to Full scale

I have a doubt regarding term "Full scale" normally used in the datasheet of energy meter ASIC (i'm using ADE7878A).

In datasheet, it has described that 0.5V is maximum voltage that can be apply to input of IC's ADC pin. Suppose i have developed a Energy meter in which i'm well sure that input will never go beyond the 0.35V.

so in this case, will 0.35V be my "Full scale" reading or ''0.5" will remain "Full scale" reading ?

Yes, it is always discussed in full scale. It is because of the proportionality of the whole loop from input up to the measurements. Everything is just a proportion.

Now, it is possible if you will not use 0.5V as your full scale, just know and understand your proportions. But if you will not maximize the use of the full scale you will be losing some accuracy, you are not utilizing the full dynamic range.

Mostly your nominal is around 50% of full scale for Voltage (the steady state), if you will use 0.35 there, your nominal is set lower to that, and you are losing accuracy on your codes or LSBs. I recommend that you design the meter in full scales of 0.5V but of course it is still your option.